The goals of this project are to establish a method of screening libraries of recombinant DNAs (CDNA or genomic DNA) using synthetic oligonucleotides as hybridization probes. The probes will be mixtures of oligonucleotides representing all possible codon combinations predicted from a particular peptide sequence within a protein. Stringent hybridization criteria will be used to allow the single correct sequence to hybridize to the correct cloned DNA. This method will be used to screen libraries of cDNA cloned in pBR322 for the clones containing cDNA for human beta-2 microglobulin and mouse H-2 Kb antigen. The cDNA clones will themselves be used to screen libraries of genomic DNA for the corresponding gene sequences.